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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>相邻兄弟选择器之常用场景</title>
  <style>
    ul {
      width: 500px;
      margin: auto;
      list-style: none;
      padding: 0;
      border: 1px solid red;
      text-align: center;
    }
    /* + 后面的元素才会起作用 */
    li + li{border-top:1px solid red;}
  </style>
</head>

<body>
<ul>
  <li>1</li>
  <li>2</li>
  <li>3</li>
  <li>4</li>
  <li>5</li>
  <li>6</li>
</ul>
</body>

</html>
